首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   20333篇
  免费   181篇
  国内免费   201篇
安全科学   534篇
废物处理   986篇
环保管理   2418篇
综合类   2667篇
基础理论   5284篇
环境理论   4篇
污染及防治   5597篇
评价与监测   1650篇
社会与环境   1453篇
灾害及防治   122篇
  2023年   92篇
  2022年   215篇
  2021年   217篇
  2020年   139篇
  2019年   177篇
  2018年   326篇
  2017年   320篇
  2016年   524篇
  2015年   362篇
  2014年   573篇
  2013年   1744篇
  2012年   672篇
  2011年   859篇
  2010年   802篇
  2009年   785篇
  2008年   886篇
  2007年   976篇
  2006年   870篇
  2005年   716篇
  2004年   723篇
  2003年   704篇
  2002年   670篇
  2001年   911篇
  2000年   631篇
  1999年   393篇
  1998年   274篇
  1997年   246篇
  1996年   291篇
  1995年   270篇
  1994年   250篇
  1993年   233篇
  1992年   240篇
  1991年   208篇
  1990年   214篇
  1989年   219篇
  1988年   197篇
  1987年   158篇
  1986年   126篇
  1985年   138篇
  1984年   169篇
  1983年   153篇
  1982年   193篇
  1981年   134篇
  1980年   119篇
  1979年   152篇
  1978年   118篇
  1977年   107篇
  1976年   100篇
  1975年   83篇
  1974年   88篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
301.
This study aims to establish a common Key Performance Indicators (KPIs) framework for reporting about the gypsum industry biodiversity at the European level. In order to integrate different opinions and to reach a consensus framework, an original participatory process approach has been developed among different stakeholder groups: Eurogypsum, European and regional authorities, university scientists, consulting offices, European and regional associations for the conservation of nature, and the extractive industry. The strategy is developed around four main steps: (1) building of a maximum set of indicators to be submitted to stakeholders based on the literature (Focus Group method); (2) evaluating the consensus about indicators through a policy Delphi survey aiming at the prioritization of indicator classes using the Analytic Hierarchy Process method (AHP) and of individual indicators; (3) testing acceptability and feasibility through analysis of Environmental Impact Assessments (EIAs) and visits to three European quarries; (4) Eurogypsum final decision and communication. The resulting framework contains a set of 11 indicators considered the most suitable for all the stakeholders. Our KPIs respond to European legislation and strategies for biodiversity. The framework aims at improving sustainability in quarries and at helping to manage biodiversity as well as to allow the creation of coherent reporting systems. The final goal is to allow for the definition of the actual biodiversity status of gypsum quarries and allow for enhancing it. The framework is adaptable to the local context of each gypsum quarry.  相似文献   
302.
A novel approach for the green synthesis of silver nanoparticles (AgNPs) from aqueous solution of AgNO3 using culture supernatant of phenol degraded broth is reported in this work. The synthesis was observed within 10 h, and AgNPs showed characteristic surface plasmon resonance around 410 nm. Spherical nanoparticles of size less than 30 nm were observed in transmission electron microscopy. X-ray diffraction pattern corresponding to 111, 200, 220, and 311 revealed the crystalline nature of the as-formed nanoparticles. It was found that the colloidal solution of AgNP suspensions exhibited excellent stability over a wide range of ionic strength, pH, and temperature. The effect of pH and ionic strength indicated that stabilization is due to electrostatic repulsion arising from the negative charge of the conjugate proteins. The AgNPs showed highly potent antimicrobial activity against Gram-positive, Gram-negative, and fungal microorganisms. The as-prepared AgNPs showed excellent catalytic activity in reduction of 4-nitrophenol to 4-aminophenol by NaBH4. By manufacturing magnetic alginate beads, the reusability of the AgNPs for the catalytic reaction has been demonstrated.  相似文献   
303.

The automobile exhausts are one of the major sources of particulate matter in urban areas and these particles are known to influence the atmospheric chemistry in a variety of ways. Because of this, the oxidation of dissolved sulfur dioxide by oxygen was studied in aqueous suspensions of particulates, obtained by scraping the particles deposited inside a diesel truck exhaust pipe (DEP). A variation in pH showed the rate to increase with increase in pH from 5.22 to about ~6.3 and to decrease thereafter becoming very slow at pH?=?8.2. In acetate-buffered medium, the reaction rate was higher than the rate in unbuffered medium at the same pH. Further, the rate was found to be higher in suspension than in the leachate under otherwise identical conditions. And, the reaction rate in the blank reaction was the slowest. This appears to be due to catalysis by leached metal ions in leachate and due to catalysis by leached metal ions and particulate surface both in suspensions. The kinetics of dissolved SO2 oxidation in acetate-buffered medium as well as in unbuffered medium at pH?=?5.22 were defined by rate law: k obs ?=?k 0?+?k cat [DEP], where k obs and k 0 are observed rate constants in the presence and the absence of DEP and k cat is the rate constant for DEP-catalyzed pathway. At pH?=?8.2, the reaction rate was strongly inhibited by DEP in buffered and unbuffered media. Results suggest that the DEP would have an inhibiting effect in those areas where rainwater pH is 7 or more. These results at high pH are of particular significance to the Indian subcontinent, because of high rainwater pH. Conversely, it indicates the DEP to retard the oxidation of dissolved SO2 and control rainwater acidification.

  相似文献   
304.
305.

The land disposal of waste and wastewater is a major source of N2O emission. This is due to the presence of high concentrations of nitrogen (N) and carbon in the waste. Abattoir wastewater contains 186 mg/L of N and 30.4 mg/L of P. The equivalent of 3 kg of abattoir wastewater-irrigated soil was sieved and taken in a 4-L plastic container. Abattoir wastewater was used for irrigating the plants at the rates of 50 and 100 % field capacity (FC). Four crop species were used with no crop serving as a control. Nitrous oxide emission was monitored using a closed chamber technique. The chamber was placed inside the plastic container, and N2O emission was measured for 7 days after the planting. A syringe and pre-evacuated vial were used for collecting the gas samples; a fresh and clean syringe was used each time to avoid cross-contamination. The collected gas samples were injected into a gas chromatography device immediately after each sampling to analyse the concentration of N2O from different treatments. The overall N2O emission was compared for all the crops under two different abattoir wastewater treatment rates (50 and 100 % FC). Under 100 % FC (wastewater irrigation), among the four species grown in the abattoir wastewater-irrigated soil, Medicago sativa (23 mg/pot), Sinapis alba (21 mg/pot), Zea mays (20 mg/pot) and Helianthus annuus (20 mg/pot) showed higher N2O emission compared to the 50 % treatments—M. sativa (17 mg/pot), S. alba (17 mg/pot), Z. mays (18 mg/pot) and H. annuus (18 mg/pot). Similarly, pots with plants have shown 15 % less emission than the pots without plants. Similar trends of N2O emission flux were observed between the irrigation period (4-week period) for 50 % FC and 100 % FC. Under the 100 % FC loading rate treatments, the highest N2O emission was in the following order: week 1 > week 4 > week 3 > week 2. On the other hand, under the 50 % FC loading rate treatments, the highest N2O emission was recorded in the first few weeks and in the following order: week 1 > week 2 > week 3 > week > 4. Since N2O is a greenhouse gas with high global warming potential, its emission from wastewater irrigation is likely to impact global climate change. Therefore, it is important to examine the effects of abattoir wastewater irrigation on soil for N2O emission potential.

  相似文献   
306.
The global extent of macroalgal forests is declining, greatly affecting marine biodiversity at broad scales through the effects macroalgae have on ecosystem processes, habitat provision, and food web support. Networks of marine protected areas comprise one potential tool that may safeguard gene flow among macroalgal populations in the face of increasing population fragmentation caused by pollution, habitat modification, climate change, algal harvesting, trophic cascades, and other anthropogenic stressors. Optimal design of protected area networks requires knowledge of effective dispersal distances for a range of macroalgae. We conducted a global meta‐analysis based on data in the published literature to determine the generality of relation between genetic differentiation and geographic distance among macroalgal populations. We also examined whether spatial genetic variation differed significantly with respect to higher taxon, life history, and habitat characteristics. We found clear evidence of population isolation by distance across a multitude of macroalgal species. Genetic and geographic distance were positively correlated across 49 studies; a modal distance of 50–100 km maintained FST < 0.2. This relation was consistent for all algal divisions, life cycles, habitats, and molecular marker classes investigated. Incorporating knowledge of the spatial scales of gene flow into the design of marine protected area networks will help moderate anthropogenic increases in population isolation and inbreeding and contribute to the resilience of macroalgal forests. Implicaciones del Aislamiento por Distancia de Macroalgas para Redes de Áreas Marinas Protegidas  相似文献   
307.
This study considers the flux of radioactivity in flowback fluid from shale gas development in three areas: the Carboniferous, Bowland Shale, UK; the Silurian Shale, Poland; and the Carboniferous Barnett Shale, USA. The radioactive flux from these basins was estimated, given estimates of the number of wells developed or to be developed, the flowback volume per well and the concentration of K (potassium) and Ra (radium) in the flowback water. For comparative purposes, the range of concentration was itself considered within four scenarios for the concentration range of radioactive measured in each shale gas basin, the groundwater of the each shale gas basin, global groundwater and local surface water. The study found that (i) for the Barnett Shale and the Silurian Shale, Poland, the 1 % exceedance flux in flowback water was between seven and eight times that would be expected from local groundwater. However, for the Bowland Shale, UK, the 1 % exceedance flux (the flux that would only be expected to be exceeded 1 % of the time, i.e. a reasonable worst case scenario) in flowback water was 500 times that expected from local groundwater. (ii) In no scenario was the 1 % exceedance exposure greater than 1 mSv—the allowable annual exposure allowed for in the UK. (iii) The radioactive flux of per energy produced was lower for shale gas than for conventional oil and gas production, nuclear power production and electricity generated through burning coal.  相似文献   
308.
Thermotolerant coliform (TC) loadings were quantified for 49 catchments draining into the North and South Bays of Santa Catarina (SC, southeastern Brazil), an area known for its tourism and aquaculture. TC loadings were calculated based on flow measurements taken in 26 rivers. TC concentrations ere quantified based on surface water samples collected at 49 catchment outlets in 2012 and 2013. Median TC loads ranged from 3.7 × 103 to 6.8 × 108 MPN s?1. TC loadings in the catchments increased in proportion to increases in resident human population, population density and percentage of urbanised area. Catchments with more than 60% of area covered by wastewater collection and treatment systems had higher TC loads per person than catchments with less than 25%. Based on the study catchments, these results indicate that current sewerage infrastructure is ineffective in reducing contamination of faecal origin to surface waters. These findings have important implications for the management of microbiological health hazards in bathing, recreational and shellfish aquaculture waters in the North and South Bays of Santa Catarina Island.  相似文献   
309.
As people encroach increasingly on natural areas, one question is how this affects avian biodiversity. The answer to this is partly scale‐dependent. At broad scales, human populations and biodiversity concentrate in the same areas and are positively associated, but at local scales people and biodiversity are negatively associated with biodiversity. We investigated whether there is also a systematic temporal trend in the relationship between bird biodiversity and housing development. We used linear regression to examine associations between forest bird species richness and housing growth in the conterminous United States over 30 years. Our data sources were the North American Breeding Bird Survey and the 2000 decennial U.S. Census. In the 9 largest forested ecoregions, housing density increased continually over time. Across the conterminous United States, the association between bird species richness and housing density was positive for virtually all guilds except ground nesting birds. We found a systematic trajectory of declining bird species richness as housing increased through time. In more recently developed ecoregions, where housing density was still low, the association with bird species richness was neutral or positive. In ecoregions that were developed earlier and where housing density was highest, the association of housing density with bird species richness for most guilds was negative and grew stronger with advancing decades. We propose that in general the relationship between human settlement and biodiversity over time unfolds as a 2‐phase process. The first phase is apparently innocuous; associations are positive due to coincidence of low‐density housing with high biodiversity. The second phase is highly detrimental to biodiversity, and increases in housing density are associated with biodiversity losses. The long‐term effect on biodiversity depends on the final housing density. This general pattern can help unify our understanding of the relationship of human encroachment and biodiversity response. Patrones Sistemáticos Temporales en la Relación entre Desarrollos Urbanos y la Biodiversidad de Aves de Bosque  相似文献   
310.
Wildlife diseases pose an increasing threat to biodiversity and are a major management challenge. A striking example of this threat is the emergence of chytridiomycosis. Despite diagnosis of chytridiomycosis as an important driver of global amphibian declines 15 years ago, researchers have yet to devise effective large‐scale management responses other than biosecurity measures to mitigate disease spread and the establishment of disease‐free captive assurance colonies prior to or during disease outbreaks. We examined the development of management actions that can be implemented after an epidemic in surviving populations. We developed a conceptual framework with clear interventions to guide experimental management and applied research so that further extinctions of amphibian species threatened by chytridiomycosis might be prevented. Within our framework, there are 2 management approaches: reducing Batrachochytrium dendrobatidis (the fungus that causes chytridiomycosis) in the environment or on amphibians and increasing the capacity of populations to persist despite increased mortality from disease. The latter approach emphasizes that mitigation does not necessarily need to focus on reducing disease‐associated mortality. We propose promising management actions that can be implemented and tested based on current knowledge and that include habitat manipulation, antifungal treatments, animal translocation, bioaugmentation, head starting, and selection for resistance. Case studies where these strategies are being implemented will demonstrate their potential to save critically endangered species. Intervenciones para Reducir el Riesgo de Extinción en Anfibios Amenazados por la Quitridiomicosis  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号